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power with line wire enter the wall switch and out going and there is no neutral

Discussion in 'General Electronics Discussion' started by moeinglory, Feb 1, 2014.

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  1. moeinglory

    moeinglory

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    Feb 1, 2014
    hi to all. i extremely need help, i want to power my micro and...... with line wire that coming to wall switch and out going from other side of wall switch and i have no neutral before my load(lamp) and the other side of the lamp going to neutral of course. what i must do?
     
  2. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Sorry didn't get a word of that. Can you send in a picture of what you want to do.
    Adam
     
  3. jpanhalt

    jpanhalt

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    Nov 12, 2013
    In some older wiring schemes, the neutral was not always brought to the switch box, particularly for 3-way switches working lights. The 2011 NEC pretty much eliminated that.

    @moeinglory, If that is the situation you have, you will need to find a neutral or use a wall socket, which should have a neutral. You must not use the ground (green) wire as the neutral.

    http://www.do-it-yourself-help.com/wiring_switches.html
    http://users.wfu.edu/matthews/courses/p230/switches/SwitchesTut.html

    In the second link, a battery symbol is used, but obviously an AC voltage source is intended.

    John
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    OK, don't crucify me for this...

    You could place a series of diodes in inverse parallel to create a voltage drop and then use this as a source of power. That power will only be available when the load is powered, and your circuit will run entirely at mains potential (that means touching it can kill you).

    This is probably not suitable if you need to run the microcontroller when the power load is not being powered.

    Oh, and the voltage to the load is reduced by a couple of volts. Depending on the load current, the diodes may need to have a significant current rating (although their inverse voltage rating is largely unimportant).
     
  5. moeinglory

    moeinglory

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    Feb 1, 2014
    Report Post Yesterday, 04:21 AM #5
    ok . firs tanx. but i cant wiring the neutral, no way, and diodes idea!!! two point first when the load is off i have my own power with the load wire that coming from load to switch thats similar to neutral and all power source work fine, and next when the load is on and powered, diodes is good idea but is that dropped fix voltage all the time?? and if the load needs huge current like 10A diodes will be work? and the most important point, would any voltage drop on diodes when just a line connect to one side and current pass through them into load??
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Using this approach you can only have power when the load is turned on. No exceptions. If you have external power, make sure it's totally self contained (like batteries) and remember that these batteries will be at mains potential whenever you have power to your house (i.e. switch off mains before changing batteries)

    Can you tell why I think it's not a great idea?

    Yes, the diodes need to be able to take the full load current (and may dissipate a fair amount of heat at 10A)
     
  7. moeinglory

    moeinglory

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    Feb 1, 2014
    battery is so bad idea!!! look. i have an ordinary switching power(like chargers) and its work good when the load is turn off. ok? and how about when the load is turned on? its my problem
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If you have a switching power supply, use that. You obviously have access to power for that to run. Use it. It's a lot safer.
     
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    I'm working on a project that does exactly this. It's a turn-off delay for a bathroom fan. The wall wiring for the fan doesn't have a Neutral wire so I have to get power for the micro by intercepting the load current. I use a triac in parallel with the switch so that the circuit can keep the fan running (and keep itself powered) until it's time to switch off.

    Here's the schematic. I haven't built it up yet; I'm still working on the code. But it should give you some idea of how it can be done.

    [​IMG]
     

    Attached Files:

  10. moeinglory

    moeinglory

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    Feb 1, 2014

    yes this is exactly what I'm looking for. by the is that work? and can we do this without pic and micro and programming? and the last you think is that work for 10A current?
     
    Last edited by a moderator: Feb 4, 2014
  11. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    What? Are you asking whether it works? I haven't built it up so I can't say for sure, but I'm certainly expecting it to work!
    That depends on how you want to control the triac. For my project, I decided that you would be able to select from several different fan turn-off delays by switching the wall switch ON and OFF one or more extra times before leaving it to do its thing. It would have required a lot of discrete logic to implement that feature, so I decided to use a microcontroller. I also designed a version that doesn't use a microcontroller, and provides a single time delay, but it has three ICs instead of just one.
    Well, you could replace D1~9 and Q1 with bigger devices, yes. This diode looks suitable: http://www.digikey.com/product-detail/en/BYV79E-200,127/568-3440-ND and this triac: http://www.digikey.com/product-detail/en/BT139-600,127/568-3665-5-ND

    What is the load you want to control, and how do you want to control it?
     
  12. moeinglory

    moeinglory

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    Feb 1, 2014
    at firs tanx alot really for your help and answers.
    actually i want to control a wall switch and the end of big garden in faaar away with wireless control , so i have the electronic switch at all,made by me!!!:) and its connect to 2200watt pump for water pumping. so i havent micro controller and i want the power for 2 mode 1.loade is off 2.load is on. the mode 1 is easy . and your suggest is good for time load is on(mode 2) and i prefer do not use micro and programming. whats 3 ICs you talking about? op amp and so on?
     
  13. moeinglory

    moeinglory

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    Feb 1, 2014
  14. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    So you have a wall switch that controls a 2200 watt water pump, and you want to be able to switch it ON remotely using a wireless remote control?
    And you've made the wireless receiver? Can you post a schematic of it? What power source does it need?
    I don't understand.
    No, the non-microcontroller version of my my fan timer circuit uses 1x CD4093B and 2x CD4040B. It uses the mains supply as the timing source and the fan turn-off delay can be set from a few minutes to a few hours using a DIP switch. This is not relevant to your application though, because you want to use a remote control, not a timer. You need to give us some information on your remote control receiver.
    I don't understand. Those links work OK for me.
     
  15. moeinglory

    moeinglory

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    Feb 1, 2014
    yes look i have an ordinary RF transmitter and in switch i have receiver and a relay but if i use triac i dont need relay any more, my RF receiver need 5 volt and about 200 mA current power supply and i hope i can use your method to power my circuit. and on-off my switch and water pump remotely. you tell me your method can give me 5 volt and 200 -300 mA when the load (water pump) is on? and i use this supply to keep my circuit alive and send off order to my switch to cut off the pump.
     
  16. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    My method cannot be used to switch the load ON. The circuit only receives power while current is flowing in the load. Something must start that current flowing, and it cannot be the circuit, because while the pump is not running, the circuit has no power, so it cannot switch itself on.
     
  17. moeinglory

    moeinglory

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    Feb 1, 2014
    yes yes. i know that. thats the reason i told i use a switching power while the load is OFF to running the pump
    (turn it on) then for turning it OFF using your method to keep the power of circuit to be able recieve command to off the pump,
     
  18. moeinglory

    moeinglory

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    Feb 1, 2014
    how i must programming the micro.? it should on off triac so fast? how we must earn power? with interrupt ?? by triac?
     
  19. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If you have 5V at 200mA then that is all you need. The simplest, safest, and easiest solution is to use a relay (possibly a solid state relay) to switch your load.

    The technique that I mentioned and which Kris expanded on is only used when you have no external power source, and generally CAN'T BE USED TO TURN SOMETHING ON.
     
  20. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    So you connect a switchmode power supply across the switch, so when the switch is OFF, the power supply powers the circuit, then when the switch is ON, or the circuit is driving the triac which is in parallel with the switch, the circuit is powered by the load current using the series powering arrangement?

    Yes, I think that would be workable.
    I'm finding it quite difficult to communicate with you.

    I think you should use schematic diagrams, and more detailed explanations, to make your ideas clear.

    For your application, I don't think a microcontroller is needed.

    I don't understand your other questions.
     
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